Abstract Objective:To investigate the effect of ATP on proliferation and membrane protein expression of immortalized human fibro-blasts.Methods: Applying the normal human fibroblast cell line TIG-7 and OUMS-36, the immortalized human fibroblast cell line KMST-6 andSUSM-1 to culture 24 h and 96 h with the different concentration of ATP, ADP and AMP respectively, observed the number of cells alive, DNAsynthesis and the expression of [32 P]-ATP labeled proteins in the membrane fraction. Results: After 96 h cultured, the proliferation inhibition ofimmortalized cells exposed to 0.4 mmol/L ATP was 77% compared with that of the control cultures,while that of normal OUMS-36 cells treatedwith the same concentration was 41%;the DNA sythesis of the immortalized cells exposed to 0.4 mmol/L ATP was greater suppressed thanthat of normal OUMS-36 cells. Treated the immortalized cells with ADP, AMP, adenosine, and phosphoric acid, ADP could reducee the number ofcells significantly(P